Disaster information must be shared quickly by all the concerned people. At present, such disaster information is distributed to people by mass media. However, enabling people to share any kind of information related to disaster is one of today's most urgent issues.
The Internet is an effective tool for distributing information. However, using the Internet to distribute disaster information would not be effective, as mass disaster information would be distributed to people without distinction. Consequently, people might receive so much information that truly necessary information could be lost. Furthermore, receiving so much information might cause people to lose their interest and become insensitive even to disaster information.
Disaster information covers a spectrum ranging from ordinary disasters such as fires, weather-caused (heavy rains, lightning, snowfalls, and so forth) damages, railway accidents, and traffic accidents, through more serious natural disasters (earthquakes, eruptions, tsunamis (seismic sea waves), typhoons, and so forth) that occur only once in many years. It is therefore important not to let people overlook really necessary disaster information among a mass of information they might receive. When an existing Internet system is employed for distributing such disaster information, however, it is required to set conditions for registering customers so as to receive disaster information one by one. For example, conditions to be set could become complicated as follows. When a disaster occurs far away, what information do customers want to have? Do they need railway operation information and/or weather reports? When a disaster occurs in the neighborhood, what scale disaster information do they receive? Do they want information about small fires, traffic accidents, as well? Actually, there is no need to set the conditions in such detail, as conditions will be set coarsely so as to distribute mass information; existing systems cannot distribute truly necessary information to individual customers.